Conventionally, on an operation portion of audio equipment, a mobile phone, or the like, an input device for inputting numbers or indicating directions is placed. As one kind of the input device, there is known a direction indicator key having a push-button switch structure. In the input device of this kind, as disclosed in, for example, Patent Literature 1 and the like, a lateral direction of a “direction key” corresponds to the lateral direction of a screen of a display section. In other words, for processing represented by icons indicating a left side and a right side of a display screen, operation keys (operation portions) arranged and aligned in the lateral direction are allocated.
However, nowadays, as an electronic device becomes more multifunctional, more operation items are provided. Thus, it is necessary to reliably realize the various operation items. Accordingly, along with a recent improvement of technologies, a touch-panel-type input device has been developed. The touch-panel-type input device reads movement of a finger lightly touching a touch panel, and converts the movement into a signal. Thus, it is unnecessary to strongly press the touch panel by a finger unlike a case of a push-button switch.
Further, in recent years, there is known an input device capable of detecting user's pressing direction and pressing amount using a pressure sensitive member (for example, see Patent Literature 2). Moreover, by making an operation surface of the input device annular, such a control disk is obtained as to allow easy screen shift and the like when a finger continuously touches and slides on the annular operation surface (for example, see Patent Literature 3). The control disk of Patent Literature 3 includes: a control board which is arranged on an inner surface side of a slide key as an operation part and has a pan-shaped inclined surface increasing in diameter toward the slide key around a center axis of the slide key; and a sheet made of an elastic material. In the sheet, a countersink recess for mounting and holding the control board is formed in an upper surface thereof, and an annular protrusion having a cylindrical cross-section is formed on a lower surface thereof correspondingly to a position of a pan-shaped inner peripheral surface of the recess. Through operation of the slide key, the inclined surface situated in the operating direction is pressed by the slide key, and due to the pressing, the pan-shaped inner peripheral surface of the sheet is pressed through the control board. Thus, the protrusion is structured to press the pressure sensitive member arranged below the protrusion.